Observations of the space‐time structure of flow, turbulence, and stress over orbital‐scale ripples. Issue 3 (13th March 2014)

• Record Type: Journal Article
• Authors: Hare, Jenna; Hay, Alex E.; Zedel, Len; Cheel, Richard
• Is Part Of: Journal of geophysical research. Volume 119:Issue 3(2014:Mar.)
• Page Start: 1876
• Page End: 1898
• Publication Date: 2014-03-13
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2013JC009370
• Languages: English
• ISSNs: 2169-9275

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>The spatial and temporal structure of flow, turbulence, and stress over equilibrium orbital‐scale sand ripples are investigated at turbulence‐resolving scales with a wide‐band coherent Doppler profiler (MFDop) and an oscillating tray apparatus. The oscillation period and horizontal excursion were 10 s and 0.5 m. A single trial was also executed at 0.6 m excursion. Ripple wavelength and amplitude were 25 and 2.2 cm. Ensemble‐averaged velocity profiles were acquired with 3 mm vertical resolution at 42 Hz. The spatial pattern of flow as a function of oscillation phase was determined by combining the phase‐averaged velocity measurements from trials with the MFDop at different positions relative to a particular ripple crest. The MFDop measurements are used to investigate the coevolution of the lee vortex, turbulent kinetic energy, Reynolds stress, and turbulence production as a function of phase. Shear stress is determined from the vertically integrated vorticity equation and the double‐averaged momentum equations. Friction factors obtained from the two methods are comparable and range from 0.1 to 0.2.</p> </abstract>